The projectile of a 40 mm grenade round weighs approximately 240 g. The projectile of a 40 mm high velocity grenade round is launched by a firing weapon at a velocity of approximately 240 meters per second. A 40 mm grenade round comprises, broadly, a projectile and a case which houses a propulsion system. The propulsion system is typically referred to as a “high-low” system. A high pressure propellant chamber is provided in the base of the case, in which pressures exceed 190 MPa in the case of a 40 mm high velocity grenade round. The propellant chamber has one or more openings at one end, which lead into a low pressure chamber. The openings are closed by means of a burst diaphragm.
An initiating primer is contained in a primer chamber at an opposite end of the propellant chamber. A mechanical striker of a firing weapon is used to initiate the primer which then causes the propellant within the high pressure chamber to combust which in turn generates high pressure gases causing the burst diaphragm to rupture and expanding propellant gases to enter the low pressure chamber. The relatively low pressure gases act on the rear end of the projectile causing it to be propelled along the barrel of a firing weapon.
The applicant is aware of a problem encountered with conventional high velocity 40 mm grenade rounds wherein the primary chambers of such grenade rounds have been known to fail due to the high pressures to which they are subjected when the propellant charge initiates. Such failures can result in damage to, or destruction of the firing weapon and also possibly result in serious injury or fatality of the operator of the weapon.
It is an object of the present invention to ameliorate the problems described hereinabove with conventional grenade rounds.